The Hangover movies make stag night seem like a harmless (if insane) male ritual. But the reality is a woman's worst nightmare.

Three days before his wedding, Adam set foot in a strip club, the location of his bachelor party. All the 37-year-old expected to get was a few lap dances — but then his buddies upped the ante. "It became apparent that this strip club was a brothel," he says. "Men would vanish with women across the street to a hotel, and return later. My friends asked, 'How much?' then started goading me."

At first, Adam hesitated: How could he cheat on his fiancée — especially in front of all these people, some her family members? Still, he reasoned, "This would be my last chance to touch another woman ever again. Being drunk and rising to their taunts, I picked a statuesque blonde with fake breasts and took a trip across the street." The sex, he says, was amazing — so much so that his fiancée didn't enter his mind until he was walking back to the club. At that point, he panicked, wondering how people would react. "If they had greeted me with averted eyes, I would have been really nervous," he says. "Instead, everyone burst into cheers, as if I'd walked in with a Nobel Prize." Before ending the night, the men devised a plan to conceal Adam's infidelity. "We agreed to overload the women with stories, except that one thing, so they'd assume they knew everything," he says. The next day, the women grilled their guys, but no one caved. "Their solidarity and confidentiality amazes me to this day," says Adam. "Her friends and family were there, and no one breathed a word."

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Bachelor parties have always had a bad rap. But with movies like The Hangover Part II celebrating just how wild this pre-wedding ritual can get, it's clear that many men see this night as an anything-goes event — even a socially acceptable chance to stray. Some men insist that infidelity in this context is no big deal, although their partners may disagree. But women rarely find out the truth. So what the hell goes on at these parties, anyway?

While not all bachelor parties include sex, the combination of booze, male bravado, and strippers is a heady mix that moves some men to do things they'd never do otherwise. As Jack, 37, explains about a bachelor party he attended, "I assumed strippers would paw me, then I'd go home and have sex with my wife," he says. "But after the stripper got me excited, she said, 'For $100, I'll finish you off.' It was like Zeus reaching down from heaven. When a girl is literally unzipping your pants, men can't say no. We're not built that way." That was the only time Jack has cheated on his wife, and he doesn't plan to again. "The opportunity is rare," he says. "You're only visiting a strip club when a guy gets dumped or engaged."

A few men admit that bachelor parties are a pressure-fueled situation that makes some feel like they have no choice but to cheat, like Sam, 42, who attended a bachelor party with two strippers. "The groom wasn't into it, so they picked me to fill in," says Sam. "The strippers both gave me oral sex while people threw cash on top of us and high-fived me. It was like I was starring in my own porno. With everyone chanting, 'Do it!' you can't say no."

Sometimes the sex is premeditated. Take Kevin, 29, who embarked on a "sexual scavenger hunt" during a bachelor party in Montreal. "We said we'd have sex with a stripper, a bride-to-be, a cougar, etc.," says Kevin. "Two guys were married, one engaged, one single, and one with a girlfriend, like me. I slept with a stripper (full point) and kissed a bride-to-be (half point)." Kevin admits that bachelor parties are male bonding at its worst: "It was a twisted celebration of our bond, another chapter in our history," he says.

Do these guys feel guilty during or after the act? Not really, since to them, it's not exactly cheating: The women are merely part of a rite of passage. It's a strange ritual, but no more bizarre than a wedding itself, argues Travis, 39. "You're pledging your entire life to one person, in a church with statues of bleeding people, and you're spending a fortune," he says. "The process is surreal, so it sets you up for anything." So when his pals hired two strippers for his bachelor party, Travis went for it. "I let my friends take control because I didn't want to be responsible," he says. "It was depraved, but at least it's out of my system."

Perhaps this is the crux of the ritual — for some men, bachelor-party sex is anticlimactic, even depressing, and sends them running back into the arms of their fiancées. Suddenly, marriage and fidelity seem appealingly wholesome. Afterward, Travis admits, "It wasn't so great compared to life with my fiancée," adding, "My wedding day was then — and still is — the best day of my entire life." And he's been faithful ever since. You believe him, right?